Electromagnet



y 2 A. w. BEDFORD, JR 2,595,755

ELECTROMAGNET Filed May 24, 1949 Inventor": Alexander BedforcLJr:

J His Attorne s.

Patented May 6, l952 ELECTROMAGNET Alexander W. Bedford, Jr., Schenectady, N. 'Y.

assignor to General Electric Company, a corporation of New York Application May 24, 1949, Serial'No; 94,965

2 Cl im 1 My invention relates to electromagnets, and more particularly to electromagnets of the solenoid type. Such devices typically include a generally ring-shaped magnetizable frame having a plunger opening at one side, a plunger, and an energizing winding disposed within the frame ring.

Conventional solenoids of the foregoing type are generally provided with a substantially rectangular frame formed of punched out laminations riveted together and provided with a plunger opening at one side. In such electromagnets the frame structure is the main supporting member for the entire electromagnet, the coil and coil spool being mounted on the frame and the frame being provided with mounting feet or the like for attachment of the electromagnet to a supporting base. While such a structure is quite simple and economical to manufacture and reasonably durable and rugged in operation, it has certain inherent disadvantages which it is the object of my present invention to overcome.

It is a principal object of my invention to provide a new and improved solenoid type electromagnet having appreciably less eddy current and hysteresis loss than has heretofore been obtainable.

Another object is to provide a novel electromagnet having a frame structure arranged to make optimum utilization of grain orientation in the steel.

It is a further object of my invention to provide an electromagnetic solenoid structure comprising a laminated frame which is devoid of rivets and mechanical strain.

It is still another objectof my invention to provide a new and novel laminated frame structure for an electromagnetic solenoid in which optimum use of the grain orientation in the laminations may be made and in which no cold working or stress of the laminations after annealing is necessary.

In accordance with my invention, the above and other objects are attained and numerous advantages realized by utilizing as the main supporting structure for the electromagnet the coil or spool body, rather than the magnetizable frame. The spool body includes mounting means for the entire structure, and on the spool body are mounted both the coil and the frame. The frame is a ring-shaped member of magnetizable material, suitably formed by continuous winding of strip material into a laminated ring with the various laminations of the ring cemented together. This ring-shaped frame member is mounted 2 upon the spool body in mutually perpendicular axial relation with respect to the coil,:and is held on the spool by means of a clamping ring surrounding the frame.

My invention itself Will be more fully under stood and its various objects and advantages further appreciated by referring now to the following detailed specification taken in conjunction with the accompanying drawing, in Fig. 1 is a side elevational view of an electromagnetic structure embodying my invention; Fig. 2 is a front elevational view of the structure shown at Fig. 1; Fig. 3 is an exploded perspective view of the same structure omitting the magnetiza'ble core member; Fig. 4 is a fragmentary perspective view of a portion of the frame structure and a modified form of plunger stop; and Fig. 5 is a front elevational view of another embodiment of my invention.

Referring-now to the drawing, and particularly to Figs. 1, 2, and 3, I have shown an electromagnetic solenoid embodying my invention and including a coil spool, or spool body, formed of a hollow tubular coil form It and a pair of oppositely disposed end shields or plates II and I2. Preferably, the entire coil spool, including the form ID and end shields I I and I2, is formed of a suitable non-magnetizable metal, such as brass or the like. In the illustrated embodiment of the invention, the coil form ID is of substantially rectangular cross section and is hollow to provide an axial passageway therethrough to receive a movable plunger. The coil form I0 is split longitudinally at Illa in order to prevent the formation of a closed electric conducting path around the plunger. Each of the end shields H' and i2 is provided with a rectangular aperture Ila and [2a, respectively, arranged to fit over the end of the coil form It. The end shields ll and-l2 are also split laterally at 1 lb and [2b to prevent the formation of a closed electric conductingpath peripherally around the rectangular apertures Ho and 12a, respectively. The end shields l l and I2 are brazed in place near opposite ends of the coil form ID to provide an integral coil spool or spool body.

The coil spool described in the foregoing paragraph serves as the main supporting element for the entire electromagnet, and to this end each end shield I I and I2 is provided with a projecting mounting foot or bracket [3, preferably formed integrally with the end shield and adapted for mounting the coil spool on a suitable supporting base I4, as shown at Fig. 1. The mounting brackets may, of course, be separate pieces brazed or otherwise suitably attached to the coil spool.

Supported upon the coil spool H), ll, 12 between the end shields H and I2 and surrounding the coil form 10, is an energizing winding or coil 15 formed of electric conducting wire. The coil l5 may be pre-wound and pre-formed, in which case it is placed over the tubular coil form [0 before the end shields H and I2 are brazed in place. the construction of light-weight units, brazing can be dispensed with by providing ears or other suitable mechanical interconnection at opposite ends of the tubular coil form [0, which ears can be swaged over the end shields H and I2 to hold the spool body and coil together. It is also within the contemplation of my invention to form the spool body as a bronze die casting, and subsequently wind the coil i5 about the tubular section thereof. Similarly, the spool body may be formed of a suitable molded plastic insulating material.

In accordance with my invention, a frame member I6 is formed as a ring of magnetizable material and mounted upon the coil spool, or spool body, in mutually perpendicular axial relation with respect to the coil IS. The ring-shaped frame [6 is apertured at one side, as at 160., adjacent one end of the axial passageway in the spool body and in alignment therewith. This aperture permits entry of an axially movable plunger il into the passageway in the spool body. In the form of the invention shown, the ring-shaped frame member 16 is mounted upon the end shields II and I2, and is disposed in positioning 1* notches H0 and 20 in the end shields H and I2, respectively. The frame I5 is held firmly in place on the spool body by a clamping ring l8, which surrounds the frame I6 and is provided at the top with a pair of turned-up ears drawn together by a bolt I9.

In alternating current electromagnetic structures it is necessary that the magnetizable frame be formed of laminated material, and in such structures I avoid the energy losses common to riveted laminated structures by forming the frame [6 as a continuously fiatwise wound spiral of flat strip material, such as silicon steel or the like. By so forming the core, I am able to select material with an optimum grain orientation. In winding such a laminated spiral core, I preferably coat the strip with a cementitious substance having insulating as well as bonding characteristics, so as to provide a unitary laminated frame member which will hold its preformed shape after winding. After the laminated frame is thus wound, it is apertured or split at one side to form a plunger opening, and is spread slightly to position it on the spool body. After the frame is thus positioned on the spool body, the clamping ring 18 is placed in position and tightened to fix the frame in place.

It will be noted from Fig. 2 that the tubular coil form I0 extends an appreciable distance below the end shield IE on the open side of the frame, and that the end of the split ring-shaped frame l6 abuts the sides of the coil form Ill. The coil form 10 thus prevents the clamping ring 18 from drawing the ends of magnetizable frame I6 into frictional engagement with the plunger tween the upper end of the plunger 11 and the It will, of course, be understood that in 1 frame [6, and also in order to provide an end stop, or anvil, for limiting upward movement of the plunger, I provide a closure member or plug 20 of magnetizable material disposed between the upper end of the spool body and the upper side of the frame [6. Preferably, the closure member i9 is formed as a plug having a portion protruding a small distance into the axial passageway in the spool body and having an enlarged head portion outside the end shield l 1 over which the frame member lies in fiatwise engagement to complete a magnetic flux path. Such a closure member or plug 20 formed of solid magnetizable material is shown at Fig. 3.

At Fig. 4, I have shown another form of closure member or plug 20, formed of laminated material and provided with a slotted head portion arranged for interfitting engagement with the ring-shaped frame structure Hi.

In order to avoid humming of the electromagnet due to vibration of the plunger, the magnetic circuit is provided with a shading coil. This coil may suitably be set into the anvil or spool closure 20, as illustrated at Figs. 3 and 4.

The plunger I1 is preferably formed without the use of rivets, and is composed of a plurality of laminations held together by a plurality of transverse welds Ila and Ilb, as illustrated at Fig. 3. Such a welded laminated electromagnetic structure is more fully described and claimed in the copending application of George B. Holland, Serial No. 755,368, filed on June 18, 1947, now abandoned, and assigned to the same assignee as the instant application.

At Fig. 5, I have illustrated another embodiment of my invention, in which the spool body ii], i 5, l2 and the coil l5 are both generally similar to that heretofore described, but in which the magnetizable frame consists of a pair of C-shaped magnetizable members 22, 23 mounted on the spool body in face to face opposing relation and encircling opposite halves of the coil 15. It will, of course, be appreciated that so long as the plane of each G-shaped core member 22, 23 includes the coil axis, an exact diametrically opposed relation of the cores is not essential. The magnetizable core members 22 and 23 illustrated in Fig. 5 may be formed as continuously wound spirals of fiat strip steel held together by interlaminar bonding material as previously described. The frame members 22, 23 are apertured at one side to form G-shaped members having opposite end surfaces mutually perpendicularly disposed. The C-shaped core members 22 and 23 are mounted upon the spool body in such a way that the upper end portions of the two frame members are side by side and protrude into the upper end of the axial passageway in the spool body, thereby jointly to form a striking face 24 for the plunger H. The core members are cut with their opposite end surfaces perpendicular to the striking face 24 and arranged to abut the side of the protruding lower end of the coil form it. As in the embodiment of the invention first described, the entire core assembly shown in Fig. 5 is held together and firmly fixed in place by a clamping ring 13 drawn together at the upper end by a bolt l9. In the embodiment of the invention illustrated at Fig. 5, those parts of the device corresponding to similar parts of the device illustrated at Figs. 1-4 have been given like reference numerals.

While I have illustrated and described a preferred embodiment of my invention by way of example, many modifications will occur to those skilled in the art, and I, therefore, wish to have it understood that I intend in the appended claims to cover all such modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In a plunger-type eleotromagnet, a coil spool including a tubular coil form having an axial passageway therein and a pair of spaced-apart end shields fixed to said form, a coil of electric conducting wire wound upon said form between said end shields, and a magnetizable frame comprising a pair of C-shaped yokes of magnetizable material mounted upon said end shields in faceto-face relation in planes including the coil axis and having one pair of adjacent ends abutting the sides of said coil form at one end and the opposite pair of adjacent ends extending axially into the other end of said coil form in side-byside relation.

2. In a plunger-type electromagnet, a coil spool including a tubular coil form having an axial passageway therein and a pair of spaced-apart end shields fixed to said form at opposite ends,

mounting means on said end shields for attaching said spool to a supporting base, a magnetizto-face opposing relation and in a plane including said coil axis, said c-shaped yokes having one pair of adjacent end portions abutting the sides of said coil form at one end and their op posite pair of adjacent end portions extending axially into said passageway at the other end to form a striking face for said plunger.

ALEXANDER W. BEDFORD, J n.

REFERENCES CITED The following references are of record in the idle of this patent:

UNITED STATES PATENTS Number Name Date 1,187,313 Heiberger et al. June 13, 1916 1,552,501 Reuter Oct. 13, 1925 1,603,873 Sandell Oct. 19, 1926 1,814,563 LeTang July 14, 1931 2,275,115 Trombetta Mar. 3, 1942 2,305,415 Goff Dec. 15, 1942 2,408,211 Hodnette Sept. 24, 1946 2,462,482 Evans Feb. 22, 1949 FOREIGN PATENTS Number Country Date 7,856 Great Britain Feb. 10, 1890 of 1889 349,203 France May 17, 1905 624,241 Germany Dec. 24, 1935 539,093 Great Britain Aug. 27, 1941 

